Rutherfordium (Rf)

• Element Symbol: Rf
• Atomic Number: 104
• Atomic Mass: 261
• Group # in Periodic Table: 4
• Group Name: Transition metals
• Period in Periodic Table: 7
• Block of Periodic Table: d-block
• Discovered by: Joint Institute for Nuclear Research, Dubna, Soviet Union (1964)

Rutherfordium is a synthetic, radioactive element. It is a member of group 4 of the periodic table, along with hafnium, titanium, and zirconium, and it is considered a transition metal. Although it is grouped with these three elements, which all share similar properties, rutherfordium is unique due to its synthetic nature. While the other three elements in group 4 can be found in nature, rutherfordium cannot. It is also considered a transuranic element because it has an atomic number greater than 92, the atomic number of uranium. In addition, rutherfordium is the first of the transactinide elements, which have atomic numbers between 104 and 118 and are all named for influential chemists and physicists (save for those not yet named).

The events surrounding the discovery of rutherfordium were a subject of debate for decades, with scientists in both California and the Soviet Union claiming credit for the element’s discovery. In 1964 a team of scientists at the Joint Institute for Nuclear Research in Dubna, Soviet Union, claimed they had discovered a new element. The team, led by Georgy Flerov, had bombarded atoms of plutonium-242 with neon-22 ions, resulting in a previously unknown element (later to be known as rutherfordium-260) as well as four free neutrons. Then in 1969, scientists working at the Lawrence Radiation Laboratory at the University of California, Berkeley, began their own attempts to confirm the Dubna team’s discovery. However, because the Berkeley scientists did not have access to the equipment necessary to accelerate neon ions, they tried a different approach. Led by Albert Ghiorso, the Berkeley team instead bombarded atoms of different isotopes of californium with ions of carbon-12 and carbon-13. This process resulted in the production of four different isotopes of rutherfordium, although none of them were the same isotope produced by the team in Dubna.

Both parties independently confirmed the discovery of the element, and each believed it had earned the right to name the element accordingly. The Russian scientists wished to call the element "kurchatovium," after Igor Kurchatov, who had been the head of the Soviet Union’s nuclear research efforts; the Americans proposed "rutherfordium" in honor of the physicist Ernest Rutherford, considered to be the father of nuclear physics. Due to the ongoing disputes, the element went by the unofficial name of "unnilquadium" for decades, remaining nameless until 1997. Eventually, the International Union of Pure and Applied Chemistry (IUPAC) conducted a thorough assessment of the claims made by both teams and concluded that the teams should share the credit, but it ruled in favor the Americans’ name choice after heavy protest from the Berkeley team. In recognition of the Dubna team’s efforts, however, the IUPAC named element 105 dubnium.

Physical Properties

No observable amount of rutherfordium has so far been isolated, making many of its physical properties difficult to confirm. Therefore, the hardness, specific gravity, specific heat, thermal conductivity, and electrical conductivity of rutherfordium are all unknown. However, rutherfordium is believed to behave like its group 4 companions, and various properties can therefore be surmised based on knowledge of these other elements, especially hafnium. The color of rutherfordium cannot be confirmed, but it is most likely metallic, with a silver, gray, or white color. The standard state of rutherfordium at 298 kelvins (K) is solid, and it is predicted to have a density of about 1.7 grams per cubic centimeter (g/cm³) in this state. The melting point of rutherfordium is estimated to be about 2100 degrees Celsius (°C). Its boiling point is estimated at around 5500 °C.

Chemical Properties

Like its physical properties, the chemical properties of rutherfordium are also difficult to confirm due to the lack of observable quantities of the element. However, rutherfordium is expected to behave like, and therefore to have chemical properties similar to, the other group 4 elements, especially those of hafnium. The predicted oxidation states of rutherfordium are +3 and +4.

Rutherfordium has fifteen different isotopes, none of which are stable or naturally occurring. These isotopes range in mass number from 253 to 268. The heavier isotopes are considered to be more stable, making rutherfordium-267 the most stable isotope, with a half-life of 1.3 hours—the longest known half-life of all rutherfordium isotopes. Lighter isotopes, such as rutherfordium-259, only exist for a few seconds or less. Rutherfordium is thought to have a closely packed, hexagonal crystal structure. The isotopes of rutherfordium generally decay through spontaneous fission, a type of radioactive decay characteristic of heavy elements that produces a large amount of energy.

Applications

Rutherfordium is not found in nature because it is a synthetic element that can only be created in a laboratory. There are no practical uses for rutherfordium outside of scientific research because of the small amounts of the element that are produced, as well as its extremely short half-life.

Bibliography

Emsley, John. Nature’s Building Blocks: An A–Z Guide to the Elements. 2nd ed. New York: Oxford UP, 2011. Print.

"Facts about Rutherfordium." LiveScience. Purch, 16 Oct. 2013. Web. 27 July 2015.

Hall, Linley Erin. The Transactinides: Rutherfordium, Dubnium, Seaborgium, Bohrium, Hassium, Meitnerium, Darmstadtium, Roentgenium. New York: Rosen, 2010. Print.

Haynes, William M., ed. CRC Handbook of Chemistry and Physics. 95th ed. Boca Raton: CRC, 2014. Print.

"Rutherfordium (Rf)." Encyclopædia Britannica. Encyclopædia Britannica, 29 Apr. 2014. Web. 27 July 2015.